1. Field of the Invention
This invention relates to accelerated hardening of an unsaturated polyester resin and, more particularly, to a method of accelerating the hardening of an unsaturated polyester resin by using as a hardening accelerator a combination of (a) a zirconium and/or titanium chelate compound together with (b) a cobalt and/or manganese compound.
2. Description of the Prior Art
For cold- or warm-setting molding of unsaturated polyester resins, there have hitherto been proposed methods in which organic peroxides such as t-butyl peroxide, methyl ethyl ketone peroxide, cyclohexanone peroxide and lauroyl peroxide are used as hardeners and as hardening accelerators are used cobalt compounds such as cobalt naphthenate and cobalt octoate, manganese compounds such as manganese naphthenate and manganese stearate, vanadium compounds and compounds such as dimethylaniline and dimethyl-p-toluidine.
Of these hardening accelerators, the cobalt compounds such as cobalt naphthenate and cobalt octoate have been placed in practical use since they have high hardening acceleration capability and provide high quality cured products. These cobalt compounds, however, have disadvantages in that they cause coloring of the cured products. Further, they are limited in supply, thus increasing production costs. While manganese compounds and vanadium compounds are more easily available and cause no coloring, their hardening acceleration capability is low and it is therefore necessary to effect the hardening at high temperatures. This makes manganese and vanadium compounds unsuitable for use in many applications.